A single nasal spray could offer broad protection against a range of respiratory illnesses, including COVID-19, influenza, pneumonia, and even allergies, according to a new study published in Science. The experimental vaccine, tested on mice, has demonstrated immunity lasting for at least three months against multiple viruses, bacteria, and a common allergen.
For decades, vaccine development has focused on antigen specificity – training the immune system to recognize and respond to a particular pathogen, a principle pioneered in the late 18th century by Edward Jenner with his smallpox vaccine. This involves introducing a harmless component of the virus or bacteria to stimulate antibody production and create “memory cells” for future encounters. However, the new approach, developed by researchers at Stanford Medicine, takes a fundamentally different tack.
Reversing the Logic: Focusing on Immune Communication
Instead of attempting to train the immune system against every potential winter illness simultaneously, the Stanford team focused on how immune cells communicate with each other. “The acquired immune system is much older from an evolutionary point of view,” explains Professor Bali Pulendran, PhD, a specialist in immunology at Stanford University and co-author of the study. “It is made up of macrophages, dendritic cells, neutrophils… All provide rapid and broad protection against different microbes. However, this immune response is generally very short: it fades after a few days, or even after three weeks maximum.”
The challenge was to prolong this initial, broad immune response. The team hypothesized that activating the immune system directly within the lungs would be key. And the most effective route to reach the lungs, they found, was through the nose. This led to the development of a nasal spray vaccine. “It is crucial to go through the intranasal route,” Professor Pulendran continues. “It allows us to directly target the airway immune system and results in strong, localized immunity. A result that could not have been obtained using a more conventional intramuscular injection.”
The innate immune system, the body’s first line of defense, is “programmed” by each tissue – not by a global pathogen. By delivering the vaccine directly to the lungs via a nasal spray, the researchers were able to maintain a localized immune state, keeping white blood cells and macrophages in a constant state of alert.
A Three-Component Formula for Sustained Immunity
The nasal spray is composed of three main elements: two molecules that stimulate macrophages and other immune cells in the lungs, and a third component that activates T lymphocytes of the adaptive immune system. The T lymphocytes work to extend the duration of the innate immune response. After four doses of the nasal spray, mice demonstrated immunity against coronaviruses, including SARS-CoV-2, bacteria causing respiratory infections like Staphylococcus aureus and Acinetobacter baumannii (common hospital-acquired infections), and even exhibited reduced sensitivity to house dust mites, a common allergen.
The ability of the vaccine to reduce allergic reactions stems from the shared immune pathways involved in both respiratory infections and allergies. “Respiratory infections and allergies involve immune responses in the same tissues in the lungs,” explains Professor Pulendran. The nasal spray effectively suppressed pathological allergic inflammation while simultaneously protecting against respiratory diseases.
The study showed that vaccinated mice were protected from SARS-CoV-2 and other coronaviruses, Staphylococcus aureus and Acinetobacter baumannii, as well as house dust mites.
From Mice to Humans: The Next Steps
While the results are promising, the next crucial step is to determine if the same immune response can be elicited in humans. The protection observed in mice lasted for several months – a significant portion of their lifespan – leading researchers to hope that immunity in humans could be even longer-lasting, potentially reducing or eliminating the need for regular booster shots. However, this remains to be seen.
“This result gives hope that immunity in humans would last even longer,” the researchers noted. A full-scale clinical trial is now needed to assess the vaccine’s safety and efficacy in humans. , scientists at Stanford Medicine unveiled these findings, marking a significant step toward the long-sought goal of a universal vaccine capable of protecting against a wide range of respiratory threats.
